The objective of the research is to investigate the use of cultured lymphocytes from allogeneic, H-2-compatible donor mice for successful adoptive immunotherapy of murine (AKR) leukemia. Using limiting dilution techniques, lymphocytes from alloimmunized donor mice are maintained in culture with T-cell growth factor (TCGF). Alloimmunization-induced antileukemia-reactive cells have heterogeneous cytotoxic specificities; some are H-2 restricted and appear to be specific for non-H-2-encoded antigens, while others mediate unrestricted killing. Functionally restricted cytolytic and helper T cells with specificity for leukemic or nonleukemic cells are selected for study. Expanded cultured cells are studied in vivo for antitumor and antihost reactivity, tissue distribution, functional life-span, and sensitivity to exogenous TCGF. Current studies focus on the use of alloimmunization-induced cytotoxic T lymphocyte (CTL) clones with specificity for class I histocompatibility antigens with limited tissue distribution (e.g., Qa-1) as immunotherapeutic agents. IL-2-dependent clones retain cytolytic function and antigen specificity after in vivo passage; however, they exhibit abnormal migration patterns in both syngeneic and allogeneic hosts with a paucity of cells in lymphoid tissues. Nevertheless, cloned CTL mediate an antileukemia reaction in vivo. Additional studies focus on the nature of the target antigens on leukemia cells. Kinetic analysis of non-H-2-restricted kill of normal and leukemic lymphocyte target cells by cloned CTL is being evaluated in a manner analogous to enzyme kinetic assays. This has provided useful information on the relative affinity of effector and target cells from various sources and for comparison of target antigen density when cloned effector CTL are used. (IT)